Automatic speech recognition (ASR) is the conversion of lexical content in a human speech to data that are readable by computers. Speech recognition normally involves a complicated speech processing process including speech decoding that follows establishing a language model and a decoder network. Audio command recognition is a specific application of the ASR technology. Audio command recognition allows a user to speak out an audio command without using a keyboard, mouse, touch screen, or other input equipments. A specific system used for audio command recognition automatically recognizes the audio command, associates the recognized audio command with an instruction, and triggers an operation on a corresponding electronic device according to the instruction.
Specifically, an audio wakeup system is a typical system that utilizes audio command recognition. A user may speak out a sound signal that includes a wakeup command. The audio wakeup system receives and recognizes the sound signal spoken out by the user, and wakes up (i.e., starts up) the corresponding electronic device from a sleep mode if the wakeup command is correctly recognized. In such an audio wakeup system, the command recognition accuracy is generally evaluated based on a false recognition rate and a no-recognition rate. The false recognition rate is associated with a situation when the system erroneously wakes up the electronic device upon a sound signal that does not include the wakeup command. The no-recognition rate is associated with another situation when the system does not respond to the sound signal that includes the wakeup command (i.e., fails to wake up the electronic device). A low false recognition rate or a low no-recognition rate indicates that the system of audio command recognition is accurate and stable.
Despite acceptable performance of audio command recognition, many audio command recognition systems do not distinguish whether the audio command comes from an authorized user of the electronic device. Anyone other than an authorized user can speak and issue the wakeup command to the audio command recognition system installed on a private electronic device, and this system always responds to the wakeup command by waking up the private electronic device. The risk of false use is significantly increased and causes a threat to the security of the electronic device. It would be beneficial to have a more secure command recognition mechanism than the current practice.